Advanced material editor, confusing controls

[Ros. Riha]

on the attached image, there are two panes of the editor, that seem to control the same thing:

• Fresnel (marked red)- does it do the same on both panes? If yes, do values multiply or overwrite one the other?
• Intensity (underlined blue) obviously does control different properties, but it is called the same, so I would vote for "Transparency" and "Reflectivity" instead to prevent confusion
• Saturation (underlined green) - what is the difference between these two?

[akinlolu olugboji]

Take intensity for example and I believe it applies to all the other properties you are referring to. intensity on one side shows the intensity of the reflective property of the material while on the other side the transparency intensity on the other side.

[Roy Hirshkowitz]

All of these settings do different things.  Keep in mind that you rarely need to change any of these, and you certainly don't for water.  Here's something I just sent to Margaret at McNeel who is currently documenting the Flamingo product:

 

 

There are two fresnel settings (pronounce fray-nell) in the AutoCAD product, one on the Main (reflection) page and one on the Transparency page.  Not sure if John has incorporated the second one. 

 

Both of these offer the user some control over a phenomenon know as "fresnel reflection"-- the tendency of a material to become more reflective at glancing angles.  The one on the Main page controls the reflectivity of opaque materials (a phenomenon known as fresnel reflection of conductors), the one on the Transparency page is used by transparent materials (fresnel reflection of dielectrics.)  The transparent version works in conjunction with the IOR.  Higher IORs reflect more.  IORs of 1.0 will not reflect.

 

A "simple" explanation for the reflection one would include something like:  controls the amount of reflection automatically added to the material at glancing angles.  The transparency explanation could include something like: controls the amount of reflection predicted by the material's transparency and IOR.

 

 

 

[Ros. Riha]

Sorry, although this seems to be thorough explanation (and thanks for that!) I am still not getting it: from what I understood from your post, fresnel control on the first pane (controlling opaque materials) should get grayed out once I use any transparency on the other pane and vice versa... or do these fresnel controls somehow cooperate on materials, that are not 100% transparent?

[Roy Hirshkowitz]

Yes-- if the material is not 100% transparent then the fresnel on the first pane will control that portion which is not transparent.

 

Do keep in mind that for transparent materials, unless you're dealing with an unusual material like laminated glass (a composite of glass and a plastic coating or layer) -- I would always set the Transparency to 100% and use the color to control the absorption.  That will give you the most physically based material.  

 

 

[Ros. Riha]

maybe it is just the friday-evening-tiredness-thingy, but... I always felt nXt is a way for us, simpletons, to produce decent renderings:-) ... now I am losing my confidence:-)

So, are you saying:

1. For a water or glass, where the transparency is almost 100%, fresnel slider on the first pane does not come to play?
2. For semi-opaque glass or translucent plastics, where the transparency would be around 50%, both fresnel sliders are equally important?
3. For solid materials, only the first fresnel slider comes to play?

Hard bit to understand for me is (2) - what does it mean "portion"? should I try to set fresnel sliders the same or should they differ for these portions? Where from to start exploring?

 

Also: "use the color to control the absorption" - does it mean that the approach of George (the "water" thread) where he uses quite dark color of water to my liking is correct? Are you saying that for almost 100% transparent materials such as water I should darken the color to make them less transparent rather than to set transparency to 0.98?

[Roy Hirshkowitz]

Don't touch either of the fresnel sliders-- leave them alone.  Make glass and water 100% transparent and control the opacity by using the color.  Use accurate IORs.

[Sampdoria]

Is there some sort of visual explanation of the Fresnell effect because most stuff online is not very clear.

[Roy Hirshkowitz]

Again, don't touch these-- the standard algorithms do a good job modeling this stuff without your input.  If you must, though, I'll attach two materials.  You can manipulate their respective fresnel sliders to see what they do.  Hint:  try 0.0.

[Sampdoria]

Thanks for your effort Roy, I really appreciate it.

[Ros. Riha]

great helper, thanks